1. Technical Field
The present invention relates to a sheet manufacturing apparatus and a defibration unit.
2. Related Art
In the field of sheet manufacturing, a process for conversion into a sheet is generally preceded by a process for converting a material serving as a stock material into fibers (a defibration process). At present, a wet method using a large amount of water is what is mainly used in such a defibration step. As such, steps for water removal, drying, and the like become needed after the sheet has been formed. The added need for water, power, and large-scale utilities such as drainage equipment also makes it difficult to reduce the size of a sheet manufacturing apparatus. Therefore, it has been increasingly difficult to meet the demands of recent years for energy conservation, environmental protection, and the like.
A method where absolutely or substantially no water is used, called a dry method, has been anticipated as a method of manufacturing a sheet in place of such a conventional method of papermaking, but the current state of manufacturing sheets has not yet seen any technique that is necessary adequately established for dry manufacturing with consistency to the point of changing from the stock material to a sheet, which is the final product. The act of disaggregating a stock material such as used paper or pulp by a dry method is generally called defibration.
Japanese laid-open patent publication No. 2008-031578 discloses a rotating body for scratch-defibration intended to defibrate a continuous body of defibration object, such as a synthetic resin, and obtaining a cotton-like material. The rotating body of Japanese laid-open patent publication No. 2008-031578 is obtained when disks having saw-toothed protruding bodies are stacked and arranged so as to have such an incline that the saw-toothed protruding bodies have a helical shape. According to Japanese laid-open patent publication No. 2008-031578, a distal end part of the blades of the rotating body is set so as to have a thickness of 0.1 mm or less, and an attempt was made to obtain a cotton-like material by having the blades cut into the defibration object (see Japanese laid-open patent publication No. 2008-031578, paragraph [0026]).
However, when the features described in Japanese laid-open patent publication No. 2008-031578 are used and a rotating body is rotated in a state where blades are made to cut into a defibration object composed of the entanglement of fibers or a defibration object obtained when fibers are bound together, then the original fibers end up being shredded by the blades, and many of the resulting fibers are of a shorter fiber length than the original fiber length.
When a sheet is manufactured by such fibers of short fiber length, then there is a concern that there would be fewer fixing points where one fiber fixes to another fiber, and that the strength of the resulting sheet is not adequate.